I have heard that Marxism itself is not opposed to small business ownership, but when I see marxist speak they appear to attack all enterprise. Can you clarify?
The major thrust of Marx's critique of capitalism concerned the relationship between employer and employee. Capitalism makes that relationship exploitative: the worker produces more value by his/her labor than is returned to the worker as payment for his/her work effort. That "more value" is the origin of profit and belongs instantaneously to the employer. This critique of capitalism applies equally whether the employer has 5 or 5000 employees. However, Marx was a nuanced thinker and also well understood the struggles and contradictions between small and large businesses. He was also a careful political strategist quite willing to see the alliance possibilities for an aroused working class that could confront and defeat big business if it could construct an effective alliance with small businesses. Such an alliance wold entail compromises all around; what the worker side might then offer is to leave small capitalists free to maintain their businesses as a "capitalist sector" alongside a socialist sector where enterprises would be run democratically - one worker one vote - by all employees.